Theoretical research on a coke-resistant catalyst for the partial oxidation of methane: Pt/Cu single-atom alloys
NEW JOURNAL OF CHEMISTRY
Authors: Meng, Yuanyuan; Ding, Chuanmin; Xue, Yuyuan; Gao, Xiaofeng; Zhang, Kan; Wang, Junwen; Li, Zhe
Abstract
Cu can prevent carbon deposition on a surface due to weak adsorption, but it exhibits a high energy barrier to C-H bond activation, which means that it is not practical. Here, inspired by the catalytic properties of Pt and the strategy of single-atom alloys, a Pt1Cu single-atom alloy (SAA) catalyst is built and studied. The primary goal is to understand the alloy's catalytic activity and coke-resistant properties during the partial oxidation of methane (POM) using density functional theory (DFT). Based on the wide application of Ni-based catalysts in POM, a parallel sample using a Pt1Ni SAA catalyst is also studied. C-H bond activation and coke resistance are quantified by the activation energy barrier of CH4 dissociation and the energy barrier of C-2 formation, respectively. It is shown that the Pt1Cu SAA catalyst can promote activation of the C-H bond of CH4, without affecting the excellent coke resistance. The first C-H cleavage is promoted by the introduction of a Pt single atom, and the activation energy barrier is 1.73 eV on the Cu(111) surface, while it is 1.16 eV on the Pt1Cu(111) surface. The activation energy barrier of C-2 formation is 2.08 eV on the Cu(111) surface and 1.89 eV on the Pt1Cu(111) surface. The properties of the Pt single-alloy Cu catalyst are obviously enhanced compared with reactions on commercial Ni-based catalysts. The activation energy barrier is 1.10 eV for CH4 dissociation and 1.35 eV for C-2 formation with the Pt1Ni SAA catalyst. Coke resistance is further elucidated by the method of changes of partial density of states (PDOS) and Mulliken charges in this work. The results on the electronic properties are consistent with the thermodynamic results. A reference strategy is provided in this work to promote the activation of the C-H bond and the coke-resistant performance during POM.
Effects of adding selenium on different remediation measures of paddy fields with slight-moderate cadmium contamination
ENVIRONMENTAL GEOCHEMISTRY AND HEALTH
Authors: Xue, Tao; Liao, Xiaoyong; Wang, Lingqing; Gong, Xuegang; Zhao, Fenghua; Ai, Jinhua; Zhang, Yangzhu
Abstract
A number of remediation measures have been used in paddy fields to alleviate serious cadmium (Cd) contamination, which may pose a public health risk through the food chain. In this study, a field trial was conducted in paddy fields with slight-moderate Cd contamination to investigate the remediation effects of combined remediation measures (CRMs), including the use of Cd-safe rice (Oryza sativa L.) cultivars, water management modes (WMMs), lime application (LA), soil amendment application (SAA), and foliar silicon (Si) fertilizers. Two groups of field trials were designed including CRMs with selenium (Se) and without selenium (non-Se) application. The results show that soil measures (LA + SAA) can increase the soil pH by 0.99 and decrease the soil DTPA-extracted Cd content by 34.19% (p < 0.05). All measures used in the present study significantly decreased the Cd content in husked rice and yield, except for the WMMs; the CRMs achieved the best results, and Se application enhanced the effects of all measures. This study shows that CRMs significantly decreased the Cd content in husked rice by 58.10%; this value increased to 72.69% after Se application (p < 0.05). These results provide useful information for selecting remediation measures in paddy fields with slight-moderate Cd contamination.